diff --git a/core/models.py b/core/models.py
index adbe56c4..20cbeb4b 100644
--- a/core/models.py
+++ b/core/models.py
@@ -26,6 +26,7 @@ from __future__ import annotations
 import importlib
 import logging
 import os
+import string
 import unicodedata
 from datetime import timedelta
 from pathlib import Path
@@ -688,12 +689,20 @@ class User(AbstractBaseUser):
             .encode("ascii", "ignore")
             .decode("utf-8")
         )
-        un_set = [u.username for u in User.objects.all()]
-        if user_name in un_set:
-            i = 1
-            while user_name + str(i) in un_set:
-                i += 1
-            user_name += str(i)
+        # load all usernames which could conflict with the new one.
+        # we need to actually load them, instead of performing a count,
+        # because we cannot be sure that two usernames refer to the
+        # actual same word (eg. tmore and tmoreau)
+        possible_conflicts: list[str] = list(
+            User.objects.filter(username__startswith=user_name).values_list(
+                "username", flat=True
+            )
+        )
+        nb_conflicts = sum(
+            1 for name in possible_conflicts if name.rstrip(string.digits) == user_name
+        )
+        if nb_conflicts > 0:
+            user_name += str(nb_conflicts)  # exemple => exemple1
         self.username = user_name
         return user_name
 
diff --git a/core/tests/test_user.py b/core/tests/test_user.py
index 0fdf43c9..a87827d5 100644
--- a/core/tests/test_user.py
+++ b/core/tests/test_user.py
@@ -166,3 +166,24 @@ def test_user_invoice_with_multiple_items():
         .values_list("total", flat=True)
     )
     assert res == [15, 13, 5]
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    ("first_name", "last_name", "expected"),
+    [
+        ("Auguste", "Bartholdi", "abartholdi2"),  # ville du lion rpz
+        ("Aristide", "Denfert-Rochereau", "adenfertrochereau"),
+        ("John", "Dôe", "jdoe"),  # with an accent
+    ],
+)
+def test_generate_username(first_name: str, last_name: str, expected: str):
+    baker.make(
+        User,
+        username=iter(["abar", "abartholdi", "abartholdi1", "abar1"]),
+        _quantity=4,
+        _bulk_create=True,
+    )
+    new_user = User(first_name=first_name, last_name=last_name, email="a@example.com")
+    new_user.generate_username()
+    assert new_user.username == expected
diff --git a/subscription/views.py b/subscription/views.py
index 4abc8e83..9a39e7b0 100644
--- a/subscription/views.py
+++ b/subscription/views.py
@@ -13,7 +13,7 @@
 #
 #
 
-import random
+import secrets
 
 from django import forms
 from django.conf import settings
@@ -85,7 +85,7 @@ class SubscriptionForm(forms.ModelForm):
                     date_of_birth=self.cleaned_data.get("date_of_birth"),
                 )
                 u.generate_username()
-                u.set_password(str(random.randrange(1000000, 10000000)))
+                u.set_password(secrets.token_urlsafe(nbytes=10))
                 u.save()
                 cleaned_data["member"] = u
         elif cleaned_data.get("member") is not None: